patch 8.2.4688: new regexp engine does not give an error for "\%v"

Problem:    New regexp engine does not give an error for "\%v".
Solution:   Check for a value argument. (issue #10079)
diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index 793faaf..0b3487f 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -1649,7 +1649,8 @@
 			      {
 				  if (cur && n)
 				  {
-				    semsg(_(e_regexp_number_after_dot_pos_search), no_Magic(c));
+				    semsg(_(e_regexp_number_after_dot_pos_search_chr),
+								  no_Magic(c));
 				    rc_did_emsg = TRUE;
 				    return NULL;
 				  }